Forest-like Structure Research Articles

Improved FPT Algorithms for Deletion to Forest-Like Structures

Improved FPT Algorithms for Deletion to Forest-Like Structures

Porous Si loaded with Ag nanoparticles for ultra-broadband infrared absorption and detection

With the rapid development of semiconductor technology, silicon based infrared detector chips have been greatly optimized with the help of MEMS process. The infrared absorber, as the core part of thermal detector, requires infrared absorption characteristics such as wide spectrum and high absorption. In this paper, two kinds of porous silicon materials loaded with Ag nanoparticles (Si@AgNPs), honeycomb-like and forest-like, were constructed by chemical etching method. The experimental results and corresponding analyses illustrated that micro- and nano-porous structures of silicon with arbitrary sizes and random spatial positions can have a great guiding effect on the light waves, providing multiple reflections and scattering, allowing increased light propagation paths and generating light trapping effect, leading to enhanced infrared absorption in a wide spectral range. AgNPs are loaded, and the collective oscillation of free electrons resonates with incident photons, thereby exciting plasmon resonance effect, which can further improve the infrared absorption properties of the material. Benefiting from the synergistic effect of light trapping and plasmon resonance, the porous Si@AgNPs with honeycomb-like or forest-like structure both exhibited high absorption properties at 2.5–20 μm. Moreover, the honeycomb-like Si@AgNPs also possessed optical interference effect, which can further enhance the absorption, compared with the forest-like Si@AgNPs.

Rational design of multivalent biosensor surfaces to enhance viral particle capture.

Viral particles bind to receptors through multivalent protein interactions. Such high avidity interactions on sensor surfaces are less studied. In this work, three polyelectrolytes that can form biosensing surfaces with different interfacial characteristics in probe density and spatial arrangement were designed. Quartz crystal microbalance, interferometry and atomic force microscopy were used to study their surface density and binding behaviors with proteins and virus particles. A multivalent adsorption kinetic model was developed to estimate the number of bonds from the viral particles bound to the polyelectrolyte surfaces. Experimental results show that the heterogeneous 3D surface with jagged forest-like structure enhances the virus capture ability by maximizing the multivalent interactions. As a proof of concept, specific coronavirus detection was achieved in spiked swab samples. These results indicate the importance of both probe density and their spatial arrangement on the sensing performance, which could be used as a guideline for rational biosensing surface design.

The supported forest-like structure of PtSn as an effective deterrent for acetaldehyde formation during the electrocatalytic oxidation of ethanol

The activity and antipoisoning property are critical for commercialization of direct ethanol fuel cells (DEFCs) so must be proceeded with extreme caution while designing the new catalysts. Herein, a Pt-based catalyst is designed by templating method and employed as the electrocatalyst in the alkaline oxidation of ethanol. The comparative study exhibits the superior performance of the optimized structure; viz. Meso PtSn-1_NF than state of the art commercial Pt/C mainly related to the increasing in the electroactive surface area and the control over the morphology in the templating method. The ethanol oxidation reaction (EOR) mechanism is studied using electrochemical methods and indicates the roles of Sn in the inhibition of acetaldehyde formation during EOR resulting in the accumulation of large amounts of aldol condensation products and blockage of the active sites.

Hierarchical Superpixel Segmentation by Parallel CRTrees Labeling.

This paper proposes a hierarchical superpixel segmentation by representing an image as a hierarchy of 1-nearest neighbor (1-NN) graphs with pixels/superpixels denoting the graph vertices. The 1-NN graphs are built from the pixel/superpixel adjacent matrices to ensure connectivity. To determine the next-level superpixel hierarchy, inspired by FINCH clustering, the weakly connected components (WCCs) of the 1-NN graph are labeled as superpixels. We reveal that the WCCs of a 1-NN graph consist of a forest of cycle-root-trees (CRTrees). The forest-like structure inspires us to propose a two-stage parallel CRTrees labeling which first links the child vertices to the cycle-roots and then labels all the vertices by the cycle-roots. We also propose an inter-inner superpixel distance penalization and a Lab color lightness penalization base on the property that the distance of a CRTree decreases monotonically from the child to root vertices. Experiments show the parallel CRTrees labeling is several times faster than recent advanced sequential and parallel connected components labeling algorithms. The proposed hierarchical superpixel segmentation has comparable performance to the best performer ETPS (state-of-the-arts) on the BSDS500, NYUV2, and Fash datasets. At the same time, it can achieve 200FPS for 480P video streams.

Aboveground carbon stocks in Madagascar’s vanilla production landscape – exploring rehabilitation through agroforestry in the light of land-use history

Forests and tree-dominated land uses store large amounts of carbon stocks in plant biomass. However, anthropogenic changes in land use and land cover decrease tree cover and associated carbon stocks. Agroforestry has the potential to maintain or restore carbon in plant biomass but the amount will be influenced by various factors that may include land-use history and management practices. However, few studies explicitly address how these factors determine aboveground carbon stocks. Therefore, our study estimates aboveground carbon stocks in different land-use types, across stem diameters and geographic origin of tree species, and its structural controls. We particularly focus on the importance of land-use history in agroforestry systems. We conducted the study in the mosaic landscape of north-eastern Madagascar in old-growth forests, forest fragments, woody fallows, and vanilla agroforests. The agroforests differed in land-use history and were either directly derived from a forest or a woody fallow after slash-and-burn shifting cultivation. Aboveground carbon stocks were highest in old-growth forests and lowest in woody fallows. Within vanilla agroforests, aboveground carbon stocks were highly variable: forest-derived agroforests stored significantly higher carbon stocks that were mainly stored in native and endemic species, whereas fallow-derived agroforests stored lower carbon stocks that were mainly provided by introduced species. Furthermore, aboveground carbon stocks were mainly controlled by stem density and stem diameter. In conclusion, forest-derived agroforests have the potential to maintain relatively high carbon stocks and a forest-like structure in the landscape, whereas fallow-derived agroforests contribute to converting historically forested open land into permanent tree-dominated land-use systems, thereby restoring carbon stocks. Thus, considering the land-use history of agroforests is important for conservation and restoration agendas.

Understanding the Role of Endothelial Glycocalyx in Mechanotransduction via Computational Simulation: A Mini Review.

Endothelial glycocalyx (EG) is a forest-like structure, covering the lumen side of blood vessel walls. EG is exposed to the mechanical forces of blood flow, mainly shear, and closely associated with vascular regulation, health, diseases, and therapies. One hallmark function of the EG is mechanotransduction, which means the EG senses the mechanical signals from the blood flow and then transmits the signals into the cells. Using numerical modelling methods or in silico experiments to investigate EG-related topics has gained increasing momentum in recent years, thanks to tremendous progress in supercomputing. Numerical modelling and simulation allows certain very specific or even extreme conditions to be fulfilled, which provides new insights and complements experimental observations. This mini review examines the application of numerical methods in EG-related studies, focusing on how computer simulation contributes to the understanding of EG as a mechanotransducer. The numerical methods covered in this review include macroscopic (i.e., continuum-based), mesoscopic [e.g., lattice Boltzmann method (LBM) and dissipative particle dynamics (DPD)] and microscopic [e.g., molecular dynamics (MD) and Monte Carlo (MC) methods]. Accounting for the emerging trends in artificial intelligence and the advent of exascale computing, the future of numerical simulation for EG-related problems is also contemplated.

Preparation of Tubular Forest-like and Other Carbon Structures Using Distinct Carbon Sources and Catalyst Concentrations.

In this work, various carbon nanotubes (MWCNTs) were synthetized by the spray pyrolysis method. Resulting nanoforest-like and bamboo-like carbon nanotubes, as well as Yjunctions of carbon nanotubes, possess different shapes and morphology, depending on the kind of carbon source used and on the number of iron particles on the furnace tube surface, which derives from various concentrations of ferrocene catalyst. We used the spray pyrolysis method, using different carbon sources (n-pentane, n-hexane, nheptane, and acrylonitrile) as precursors and two different concentrations of ferrocene as a catalyst. Reactions of hydrocarbon decomposition were carried out at 800oC. The solution (hydrocarbon and catalyst) was introduced with a syringe, with a flow of 1 mL/min and the synthesis time of 20 min. Argon was used as carrier gas (1000 L/min). Preheater and oven temperatures were selected 180°C and 800°C, respectively, for each carbon source. The solution passed into a quartz tube placed in an oven. According to the studies of carbon nanostructures, obtained from different precursors, it can be proposed that the structures synthesized from n-pentane, n-hexane and n-heptane are formed by the root growth method. The growth mechanism of MWCNTs was studied, confirming that the root growth formation of products takes place, whose parameters also depend on furnace temperature and gas flow rate. Dependence of interlayer distance (0.34-0.50 nm) in the formed MWCNTs on precursors and reaction conditions is also elucidated. The formation of carbon nanotubes does not merely depend on carbon precursors but also has strong correlations with such growth conditions as different catalyst concentrations, furnace temperature and gas flow rate. Such parameters as the amount of catalyst and synthesis time are also needed to be considered, since they are important to find minor values of these parameters in the synthesis of forest-like carbon nanotubes and other structures such as bamboo-like carbon nanotubes and Y-junctions in carbon nanotubes. As a result of the evaluation of interlayer distance in CNTs formed from different carbon sources, a standard value of interlayer distance normally for CNTs is 0.34 nm and for pentane A (0.5 wt.%), hexane B (1 wt.%), toluene A (0.5 wt.%) the range is from 0.33 to 0.35 nm. In case of pentane and acrylonitrile, under an increase of the catalyst concentration, an increase of the value of interlayer distance takes place from 0.35 and 0.4 to 0.4 and 0.5 nm, respectively, but for hexane, heptane and cyclohexane, an increase of the catalyst concentration maintains the same interlayer distance. This involves the use of lower quantities of raw materials and, therefore less cost for obtaining these materials.

Grid-based DBSCAN: Indexing and inference

DBSCAN is one of clustering algorithms which can report arbitrarily-shaped clusters and noises without requiring the number of clusters as a parameter (unlike the other clustering algorithms, k-means, for example). Because the running time of DBSCAN has quadratic order of growth, i.e. O(n2), research studies on improving its performance have been received a considerable amount of attention for decades. Grid-based DBSCAN is a well-developed algorithm whose complexity is improved to O(nlog n) in 2D space, while requiring Ω(n4/3) to solve when dimension ≥ 3. However, we find that Grid-based DBSCAN suffers from two problems: neighbour explosion and redundancies in merging, which make the algorithms infeasible in high dimensional space. In this paper we first propose a novel algorithm called GDCF which utilizes bitmap indexing to support efficient neighbour grid queries. Second, based on the concept of union-find algorithm we devise a forest-like structure, called cluster forest, to alleviate the redundancies in the merging. Moreover, we find that running the cluster forest in different orders can lead to a different number of merging operations needed to perform in the merging step. We propose to perform the merging step in a uniform random order to optimize the number of merging operations. However, for high-density database, a bottleneck could be occurred, we further propose a low-density-first order to alleviate this bottleneck. The experiments resulted on both real-world and synthetic datasets demonstrate that the proposed algorithm outperforms the state-of-the-art exact/approximate DBSCAN and suggests a good scalability.

A facile one-step hydrothermal approach for the synthesis of a CuMoO4/MoS2 composite as a high performance pseudocapacitive material for supercapacitor applications

CuMoO4/MoS2-nanoparticle forest-like structures exhibit a very good specific capacitance and cyclic stability compared to the CuMoO4 and MoS2 electrodes.

Mechanical properties of individual nanorods and nanotubes in forest-like structures

We calculated the mechanical properties of a ZnO nanorod within forest-like samples. According to the results for ZnO nanorods, we extended the calculation method to determine the mechanical properties of a TiO2 nanotube (TN) extracted from a forest densely grown by anodization on a Ti substrate. The Euler model was adopted, and critical-load measurements were performed during vertical-compression experiments involving nanoindentation. We measured the elastic moduli of a single ZnO nanorod and a single TN as ~190 and ~27GPa, respectively. Thus, we suggested a method for determining the mechaical properties of individual entities in one-dimensional materials grown in bundles.

Sub-5 μm balls possessing forest-like poly(methyloxazoline)/polyethyleneimine side chains and templated silica microballs with unusual internal structures

Herein, sub-5 μm microballs, with unusual forest-like structures consisting of a polystyrene network and forest-like poly(2-methyl-2-oxazoline) (PMOZ) and/or linear polyethyleneimine (LPEI) side chains, were synthesized by combining two isolated processes.

Posibilidades financieras de diversificación en cafetales mexicanos

Por muchos años el cultivo del café ha sido un uso altamente socorrido para tierras de vocación forestal en zonas de bosque mesófilo de montaña. En este sentido es pertinente explorar las cualidades que puedan tener las variantes del cultivo que conducen hacia un paisaje y estructuras más cercanas a la del bosque natural, tal como el caso del empleo de cultivos asociados, sea como sombra o como de cobertura. La introducción de palma camedor (Chamaedorea elegans) y de la nuez de macadamia (Macadamia spp), dentro de cafetales es una estrategia iniciada por los mismos cafeticultores. En ella, simultáneamente se aporta diversidad, tanto en un aspecto biológico, como en el sentido de enfrentar los riesgos de un mercado internacional violentamente fluctuante, característico de este grano. Análisis financieros que comparan estas dos formas de cultivo con formas intensivas donde el café es el único producto, como el café con sombra de especies forestales, el café a pleno sol, y café orgánico, hacen ver que estas opciones son económicamente viables pero financieramente inferiores al café a sol, dado el actual escenario económico, justificándose el policultivo sólo para empresarios para los que los riesgos de mercados cafetaleros adversos sean inaceptables. Macadamia aparece como una inversión lo suficientemente fuerte en sí misma como para sugerir que se le desarrolle en monocultivo. La comparación asume mercados libres y establece condiciones de comparación de equidad que obligan a usar valores reales para insumos y productos, vigentes en México en la primavera de 1995, y un costo de capital privado real estimado en 5%. Los datos biológicos principales, como el rendimiento, provienen de evidencias empíricas, la mayoría mexicanas.

Module Design and Functionally Non-Isomorphic Configurations of the Hex-DMR II System

Modular robots have captured the interest of the robotics community over the past several years. In particular, many modular robotic systems are reconfigurable, robust against faults, and low-cost due to mass production of a small number of different homogeneous modules. Faults in these systems are normally tolerated through redundancy or corrected by discarding damaged modules, which reduces the operational capabilities of the robot. To overcome these difficulties, we previously developed and discussed the general design constraints of a heterogeneous modular robotic system (Hex-DMR II) capable of autonomous team repair and diagnosis. In this paper, we discuss the design of each module, in detail, and present a new, novel elevator module. Then, we introduce a forestlike structure that enumerates every non-isomorphic, functional agent configuration of our system. Finally, we present a case study contrasting the kinematics and power consumption of two particular configurations during a mapping task.

Smooth Surfaces of Constant Mean Curvature in Biology (Video Link)

Differential geometry is concerned with the calculus of smooth surfaces. The field rose to prominence through its incredible power to describe Einstein’s Theory of General Relativity, in which spacetime is considered to be a smooth four-dimensional manifold. More recently, differential geometry has been used to describe stress and strain for elastic bodies, in digital signals processing and in probability theory. Smooth surfaces appear in a variety of natural systems. This research focusses on the salvinia leaf, a floating fern whose skin has the unusual property that, when immersed in water, a stable, persistent air layer is retained on the surface of the leaf. This air-water interface is made possible by the phenomenon of surface tension and a forest-like structure on the surface of the leaf, which forms a ‘tent’ of air. This interface is a smooth surface that can be investigated using differential geometry, and has the particular property that it’s mean curvature is constant. The equation of capillary pressure, developed in the early nineteenth century by Thomas Young and Pierre-Simon Laplace, governs the system. However, the traditional formulation of the problem can be extremely difficult to solve. The project involved reformulating the Young-Laplace equation, a second-order nonlinear partial differential equation, in a coordinate independent fashion using differential geometry. Finite element analysis was then used to obtain numerical solutions for specific domain geometries. The ability to find domain geometries which form surfaces with specified properties will aid the design of effective bionic devices.

Self-Assembly of DNA Segments on Graphene and Carbon Nanotube Arrays in Aqueous Solution: A Molecular Simulation Study

Molecular dynamics simulations were performed to study the interaction of double-stranded DNA segments with the surfaces of graphene and carbon nanotube arrays in aqueous solution. Several different kinds of self-assembly phenomena were observed. First, it is found that a DNA segment can ‘stand up’ on the carbon surfaces with its helix axis perpendicular to the surfaces of graphene or nanotube arrays to form a forestlike structure. Second, a DNA segment can also lie on the carbon surface with its axis parallel to the surface if both of its ends can form stable structure with the carbon surfaces. In the latter case, the ending basepairs of the DNA are broken due to severe deformations. Third, it is observed that short DNA segments can concatenate to each other to form a longer DNA when they are placed in the grooves of nanotube bundles. The self-assembly observed in this study usually happens in less than 50 ns. Exploration on the molecular details and self-assembly mechanism indicates the primary driving force is the π stacking interaction between the ending basepairs of DNA and the carbon rings. This study confirms the dominant role of hydrophobic π stacking in the interaction between nucleotides and carbon-based nanosurfaces in aqueous environment.

Hoàng–Reed conjecture holds for tournaments

Hoàng–Reed conjecture asserts that every digraph D has a collection C of circuits C 1 , … , C δ + , where δ + is the minimum outdegree of D , such that the circuits of C have a forest-like structure. Formally, | V ( C i ) ∩ ( V ( C 1 ) ∪ ⋯ ∪ V ( C i - 1 ) ) | ⩽ 1 , for all i = 2 , … , δ + . We verify this conjecture for the class of tournaments.

Contribution of cocoa plantations to the conservation of native ants (Insecta: Hymenoptera: Formicidae) with a special emphasis on the Atlantic Forest fauna of southern Bahia, Brazil

By maintaining a forest-like structure, shaded cocoa plantations contribute to the conservation of ants that usually live in the soil, leaf litter or canopy of tropical forests. Here we synthesize the available information on the diversity and community structure of ants in shaded cocoa plantations in the Atlantic forest region of Brazil, compare ant assemblages in cocoa agroforests with forests and other forms of agriculture, and discuss how these shaded plantations contribute to the conservation of the ants in the Atlantic Forest region. We also discuss ants of economical importance and of special interest, including Camponotus, Dolichoderus, Gnamptogenys, Pachycondyla, Pseudomyrmex and other litter dwelling genera. We discuss the situation of the tramp ant Wasmannia auropunctata in the Bahian cocoa-producing region where it is considered as native, and that of the two cryptobiotic genera Thaumatomyrmex and Typhlomyrmex, as well as that of proven and possible endangered army ant and Ponerini species. A total of 192 ant species from four strata were found in extensive sampling of a cocoa plantation with a relatively simple shade canopy (comprised primarily of Erythrina). Species richness in the cocoa plantations corresponded roughly to that of low diversity native forests, and species composition of cocoa plantations was most similar to native habitats (forest and mangroves) while ant composition in other agricultural habitats was most similar to that of urban areas. Although occurrences of Wasmannia auropunctata were similar in cocoa plantations and forests, abundance of Thaumatomyrmex and Typhlomyrmex, generally thought to be rare ants, was relatively high in cocoa plantations. These results, from cocoa plantations with relatively simple shade, demonstrate the importance of cocoa for ant conservation in the Atlantic forest region of Brazil. It is likely that cocoa plantations with a greater number of vegetation strata and higher tree species richness (such as traditional cabruca plantations) provide even more important habitat for ants generally and for ant species of conservation concern.

Fallow management strategies and issues in Southeast Asia

Abstract For many upland farming communities in Southeast Asia the fallow-period is an integral part of their farming system. These fallow-based management strategies have often followed processes of nature by protecting or substituting for specific ecological functions of the natural forest. When exposed to a changing biophysical social, economic, and/or political environment, certain driving factors influence and condition farmers’ decisional behavior leading to the development of management strategies that may either protect or destroy the forest functions of the fallow. A decision to decrease the length of the fallow period may result in the disappearance of forest fallows and potentially result in degradation due to over-intensification. On the other hand, fallow management focused on improvement of the economic productivity of the fallow vegetation itself often leaves a forest-like structure intact. Examples are presented of successful and sustainable fallow-based management strategies that were developed by farming households in Southeast Asia within the context of social, economic, political, and environmental change. Key issues are identified for research and development initiatives that begin to develop in the region to work towards long-term socio-economic and environmental sustainability of fallow-based farming systems.

Morphology of and surface modification by TiO2 deposits on a porous ceramic substrate

We investigate the morphology of and surface modification by titanium dioxide (TiO2) deposits on porous ceramic substrates placed in a horizontal, tubular, hot-wall, atmospheric pressure chemical vapor deposition (CVD) reactor with titanium tetraisoperoxide (TTIP) as the precursor. The TiO2 particles are produced from TTIP through two routes: first by thermal decomposition which then kicks off hydrolysis. The deposit characteristics is found to be location dependent. Those at the reactor entrance and exit are different from that within the reactor. Within the reactor, the deposit characteristics is further found to depend strongly on the deposition temperature (Td) and is almost independent of the flow-rate and concentration of the reactant. With a Td of about 380 °C, the deposited TiO2 forms a forest-like structure with poor adhesivity to the substrate and results in an insignificant pore size reduction for the substrate. If Td drops down to about 300 °C, the deposited TiO2 forms a rock-packing structure with good adhesivity to the substrate and can reduce the pore size of the substrate from about 1–2 μm down to about 64 nm. At both the reactor entrance and exit, the deposited TiO2 are loosely-packed spherical particles of average diameter of 140–400 nm. A theory, based on whether or not the reaction is gas-phase or surface dominated, is proposed to explain the dramatic effect of Td.